USB: Add optional match for interface class to dynamic ID facility

When adding the ID of a composite device dynamically to a driver, all
hitherto unbound interfaces are bound to this driver regardless of their
class, which may not be intended.
The patch adds the option to tell the targeted interface class to a driver
via the "new_id" attribute, in addition to the device ID.
Also, it appends the ABI documentation accordingly.

Example:
$ echo "1234 2a2a ff" >/sys/bus/usb-serial/drivers/option1/new_id
will bind only vendor-specific interfaces to the 3G driver.
Signed-off-by: Josua Dietze <digidietze@draisberghof.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

Documentation/ABI/testing/sysfs-bus-usb

@@ -119,6 +119,31 @@ Description:
 		Write a 1 to force the device to disconnect
 		(equivalent to unplugging a wired USB device).
 
+What:		/sys/bus/usb/drivers/.../new_id
+Date:		October 2011
+Contact:	linux-usb@vger.kernel.org
+Description:
+		Writing a device ID to this file will attempt to
+		dynamically add a new device ID to a USB device driver.
+		This may allow the driver to support more hardware than
+		was included in the driver's static device ID support
+		table at compile time. The format for the device ID is:
+		idVendor idProduct bInterfaceClass.
+		The vendor ID and device ID fields are required, the
+		interface class is optional.
+		Upon successfully adding an ID, the driver will probe
+		for the device and attempt to bind to it.  For example:
+		# echo "8086 10f5" > /sys/bus/usb/drivers/foo/new_id
+
+What:		/sys/bus/usb-serial/drivers/.../new_id
+Date:		October 2011
+Contact:	linux-usb@vger.kernel.org
+Description:
+		For serial USB drivers, this attribute appears under the
+		extra bus folder "usb-serial" in sysfs; apart from that
+		difference, all descriptions from the entry
+		"/sys/bus/usb/drivers/.../new_id" apply.
+
 What:		/sys/bus/usb/drivers/.../remove_id
 Date:		November 2009
 Contact:	CHENG Renquan <rqcheng@smu.edu.sg>

drivers/usb/core/driver.c

@@ -45,10 +45,12 @@ ssize_t usb_store_new_id(struct usb_dynids *dynids,
 	struct usb_dynid *dynid;
 	u32 idVendor = 0;
 	u32 idProduct = 0;
+	unsigned int bInterfaceClass = 0;
 	int fields = 0;
 	int retval = 0;
 
-	fields = sscanf(buf, "%x %x", &idVendor, &idProduct);
+	fields = sscanf(buf, "%x %x %x", &idVendor, &idProduct,
+					&bInterfaceClass);
 	if (fields < 2)
 		return -EINVAL;
 
@@ -60,6 +62,10 @@ ssize_t usb_store_new_id(struct usb_dynids *dynids,
 	dynid->id.idVendor = idVendor;
 	dynid->id.idProduct = idProduct;
 	dynid->id.match_flags = USB_DEVICE_ID_MATCH_DEVICE;
+	if (fields == 3) {
+		dynid->id.bInterfaceClass = (u8)bInterfaceClass;
+		dynid->id.match_flags |= USB_DEVICE_ID_MATCH_INT_CLASS;
+	}
 
 	spin_lock(&dynids->lock);
 	list_add_tail(&dynid->node, &dynids->list);